The present invention relates to a semiconductor device and a method for producing the same that has a built-in integrated circuit section used for information communication equipment or electronic equipment for offices and allows a high-density packaging provided with wires or electrodes that connect the semiconductor integrated circuit section to the terminals of external equipment.
Recently, with compactness, high density and high functionality of electronic equipment, compactness and high density have been required for semiconductor devices. To satisfy this need, a technique to form CSP (chip size package) within semiconductor wafers has come to be used (Japanese Laid-Open Patent Publication No. 8-102466). The CSP formed within a semiconductor wafer is called a wafer level CSP even after a semiconductor wafer is divided into chips.
Hereinafter, a conventional semiconductor device and a production method thereof will be described in detail in reference with the accompanying drawings.
FIG. 5 is a cross-sectional view of a conventional semiconductor device, more specifically, a conventional wafer level CSP.
As shown in FIG. 5, in the conventional wafer level CSP, a plurality of element electrodes 101 that are electrically connected to semiconductor elements are formed on a semiconductor wafer 100 in which the semiconductor elements are arranged in respective semiconductor chip forming regions (not shown). The surface of the semiconductor wafer 100 is covered with a passivation film 102 in which a plurality of openings 102a are arranged in order to expose the element electrodes 101. On the passivation film 102, a plurality of Cu wires 103 that are connected to the element electrodes 101 via the openings 102a are formed. The surface of each of the Cu wires 103 is covered with a Ni-plated layer 104. On the passivation film 102, a cover coating film (protective film) 105 is formed so as to cover the Cu wires 103 as well as Ni-plated layer 104. In the cover coating film 105, a plurality of openings 105a are formed so as to expose a plurality of external electrodes 106 that are formed of a portion of the Cu wires 103 (including the Ni-plated layer 104) and are two-dimensionally arranged. A plurality of solder bumps 107 connected to the external electrodes 106 via the openings 105a are formed immediately above the external electrodes 106 as external electrode terminals.
The outline of a method for producing the conventional wafer level CSP is as follows.
First, a passivation film 102 is formed by spin-coating on the whole surface of the semiconductor wafer 100 provided with semiconductor elements and a plurality of element electrodes 101 electrically connected to the semiconductor elements in respective semiconductor chip forming regions. Then, a plurality of openings 102a is formed in the passivation film 102 so as to expose the element electrodes 101 by well-known techniques of photolithography and etching.
Next, a plurality of Cu wires 103 are formed on the semiconductor wafer 100 via the passivation film 102 so as to extend within the inner portion of respective semiconductor chip forming regions and to be connected to the element electrodes 101 via the openings 102a. Thereafter, a Ni-plated layer 104 is formed on the Cu wires 103 by electroless plating.
Then, a cover coating film 105 is formed so as to cover the Cu wires 103, and then a plurality of openings 105a are formed on the cover coating film 105 in order to expose a plurality of external electrodes 106 that are formed of a portion of the Cu wires 103 and arranged two-dimensionally by well-known techniques of photolithography and etching. Thereafter, a plurality of solder bumps 107 that are connected to the external electrodes 106 via the openings 105a are formed immediately above the external electrodes 106 as external electrode terminals.
As described above, according to the wafer level CSP that is a conventional semiconductor device, the external electrodes 106 that are connected to the respective element electrodes 101 can be arranged two-dimensionally regardless of the arrangement of the element electrodes 101, so that compact semiconductor device can be produced, and therefore, equipment such as information communication equipment can also be made small in size.
However, in the conventional semiconductor device, there exists a resistance in the wires connecting the element electrodes to the external electrodes (for example, Cu wires) in addition to a resistance in the wires connecting the semiconductor elements to the element electrodes (for example, Al wires). Because of the resistance, signal delay is increased and the problem is caused that high-speed transmission of signals between the semiconductor device and external equipment becomes difficult.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a semiconductor device that allows high-speed transmission of signals between the semiconductor device and external equipment while compactness is achieved.
In order to achieve the above object, a semiconductor device of the present invention includes a semiconductor substrate provided with at least one semiconductor element, a first element electrode and a second element electrode formed on the semiconductor substrate and connected electrically to the semiconductor element, an insulating film formed so as to cover the first element electrode and the second element electrode, a first opening formed on the insulating film and exposing at least one portion of the first element electrode, a second opening formed on the insulating film and exposing at least one portion of the second element electrode, a first external electrode formed immediately above the first element electrode and connected to the first element electrode via the first opening, a second external electrode formed on the insulating film and a connecting wire formed on the insulating film and having one end connected to the second element electrode via the second opening and the other end connected to the second external electrode.
The semiconductor device of the present invention includes a first external electrode formed immediately above the first element electrode and connected to the first element electrode. Therefore, the first element electrode and the first external electrode are connected without a wire, so that the resistance between the first element electrode and the first external electrode can be reduced and signal delay can be decreased. Thus, high-speed transmission of signals between the semiconductor device and external equipment becomes possible.
The semiconductor device of the present invention includes a second external electrode formed on the insulating film on the semiconductor substrate and a connecting wire formed on the insulating film and having one end connected to the second element electrode and the other end connected to the second external electrode. Therefore, regardless of the arrangement of the second element electrodes, the second external electrodes electrically connected to the second element electrodes can be arranged two-dimensionally, so that it is possible to provide multiple external electrode terminals in a small area. As a result, it becomes possible to realize a compact semiconductor device that is capable of including multiple pins.
Furthermore, according to the semiconductor device of the present invention, the first external electrode, the second external electrode and the connecting wire can be formed easily by patterning a conductive film formed on the semiconductor substrate to integrally form the first external electrode, the second external electrode and the connecting wire. Therefore, manufacturing cost can be reduced.
In the semiconductor device of the present invention, the semiconductor substrate may be a semiconductor wafer or a chip obtained by dividing a semiconductor wafer.
In the semiconductor device of the present invention, it is preferable that the insulating film is formed of elastic insulating material.
According to the semiconductor device as described above, in the case where the semiconductor device is mounted on a motherboard, even if the heating or cooling of the semiconductor device causes stress in the connection between the semiconductor device and the motherboard because of the difference in thermal expansion coefficient between the semiconductor device and the motherboard, the stress is reduced by the insulating film formed of elastic material, that is, the elastic layer. As a result, the possibility that the conductive pattern such as the external electrode or the connecting wire is disconnected is decreased, so that a highly reliable wiring structure can be realized.
In the semiconductor device of the present invention, it is preferable that each wall surface of the first opening and the second opening, or at least the portions near the upper end and near the lower end of the wall surface have an inclination of less than 90xc2x0 with respect to the surface of the semiconductor substrate.
According to the semiconductor device as described above, the conductive pattern such as the external electrode or the connecting wire never straddles a sharp step, so that the conductive pattern is easily formed and hardly disconnected.
In the semiconductor device of the present invention, it is preferable that the semiconductor device further includes a pair of third element electrodes formed on the semiconductor substrate and electrically connected to the semiconductor elements, a pair of third openings formed on the insulating film and exposing at least one portion of each of the pair of third element electrodes and a coil formed on the insulating film and having ends, each of which is connected to a corresponding third element electrode of the pair via a corresponding third opening of the pair.
In the semiconductor device as described above, a coil with high L (inductance) value that has been difficult to form by the conventional semiconductor process can be realized by patterning the conductive film formed on the semiconductor substrate to form the coil. Therefore, semiconductor elements for high frequency can also be attained.
It is preferable that the semiconductor device of the present invention further includes a protective film formed so as to cover the first external electrode, the second external electrode and the connecting wire and having the property of repelling a conductive material, a fourth opening formed on the protective film and exposing at least one portion of the first external electrode, a fifth opening formed on the protective film and exposing at least one portion of the second external electrode, a first external electrode terminal formed immediately above the first external electrode and connected to the first external electrode via the fourth opening and a second external electrode terminal formed immediately above the second external electrode and connected to the second external electrode via the fifth opening.
According to the semiconductor device as described above, when mounting the semiconductor device on the motherboard, unfavorable electrical short-circuit is prevented between the first external electrodes, the second external electrodes or the connecting wires and wirings or electrodes of the motherboard, and the semiconductor device can be reliably mounted on the motherboard.
In the case where the semiconductor device includes the first external electrode terminals and the second external electrode terminals, it is possible to use metallic balls, conductive bumps or a portion of each of the first external electrodes and the second external electrodes as the first and second external electrode terminals. However, in any case, it is preferable that the junctions of the first external electrodes and the first external electrode terminals are covered with the protective film.
In the semiconductor device of the present invention, it is preferable to further include a passivation film covering the surface of the semiconductor substrate except the first element electrode and the second element electrode and that the insulating film is formed above the passivation film.
According to the semiconductor device as described above, the reliability of the semiconductor device can be improved.
In the case where the passivation film is included, it is preferable that the semiconductor device further includes a pair of third element electrodes formed on the semiconductor substrate and electrically connected to the semiconductor elements and a coil formed on the passivation film and having ends, each of which is connected to a corresponding third element electrode of the pair, and that the insulating film covers the coil.
According to the semiconductor device as described above, a coil with high L value that has been difficult to form by the conventional semiconductor process can be realized by patterning the conductive film formed on the semiconductor substrate to form the coil, so that the semiconductor elements for high frequency can be attained.
A method for producing a semiconductor device according to the present invention includes a first step of forming on a semiconductor substrate on which at least one semiconductor element is provided, a first element electrode and a second element electrode electrically connected to the semiconductor element, a second step of forming an insulating film so as to cover the first element electrode and the second element electrode, a third step of forming a first opening for exposing at least one portion of the first element electrode and a second opening for exposing at least one portion of the second element electrode by selectively removing an upper portion of each of the first element electrode and the second element electrode in the insulating film and a fourth step of forming a conductive film on the insulating film so as to fill up the first opening and the second opening and patterning the conductive film, thereby forming form a first external electrode connected to the first element electrode via the first opening immediately above the first element electrode, and forming a second external electrode and a connecting wire having one end connected to the second element electrode via the second opening and the other end connected to the second external electrode on the insulating film.
According to the method for producing a semiconductor device of the present invention, the first external electrode connected to the first element electrode is formed immediately above the first element electrode. Therefore, the first element electrode and the first external electrode are connected without a wire, so that the resistance between the first element electrode and the first external electrode can be reduced and signal delay can be decreased, so that high-speed transmission of signals between the semiconductor device and external equipment becomes possible.
According to the method for producing a semiconductor device of the present invention, the second external electrode and the connecting wire having one end connected to the second element electrode and the other end connected to the second external electrode are formed on the insulating film on the semiconductor substrate. Therefore, regardless of the arrangement of the second element electrodes, the second external electrodes electrically connected to the second element electrodes can be arranged two-dimensionally, so that it is possible to arrange multiple external electrode terminals in a small area. As a result, it becomes possible to realize a compact semiconductor device that is capable of including multiple pins.
Furthermore, according to the method for producing a semiconductor device of the present invention, the first external electrode, the second external electrode and the connecting wire are formed integrally by patterning a conductive film formed on the semiconductor substrate. Therefore, the first external electrode, the second external electrode and the connecting wire can be formed easily and thus manufacturing cost can be reduced.
In the method for producing a semiconductor device of the present invention, it is preferable that the semiconductor substrate is a semiconductor wafer, and the method further includes a step of dividing the semiconductor wafer into chips after the fourth step.
According to the method as described above, since the external electrodes, the connecting wires or the like can be formed collectively in respective semiconductor chip forming regions of the semiconductor wafer, manufacturing cost can be greatly reduced. In the method for producing a semiconductor device of the present invention, it is also possible that the semiconductor substrate is a chip obtained by dividing the semiconductor wafer.
In the method for producing a semiconductor device of the present invention, it is preferable that the insulating film is made of elastic insulating material.
According to the method as described above, in the case where the semiconductor device is mounted on a motherboard, even if the heating or cooling of the semiconductor device causes stress in the connection between the semiconductor device and the motherboard because of the difference in thermal expansion coefficient between the semiconductor device and the motherboard, the stress is reduced by the insulating film made of elastic material, that is, the elastic layer. As a result, the possibility that the conductive pattern such as the external electrode or the connecting wire is disconnected is decreased, so that a highly reliable wiring structure can be realized.
In the method for producing a semiconductor device of the present invention, it is preferable that the third step includes a step of forming each wall surface of the first opening and the second opening, or at least the portions near the upper end and near the lower end of the wall surface so as to have an inclination of less than 90xc2x0 with respect to the surface of the semiconductor substrate.
According to the method as described above, the conductive pattern such as the external electrode or the connecting wire never straddles a sharp step, so that the conductive pattern is easily formed and hardly disconnected.
In the method for producing a semiconductor device of the present invention, it is preferable that the first step includes a step of forming a pair of third element electrodes electrically connected to the semiconductor elements on the semiconductor substrate, the third step includes a step of forming a pair of third openings for exposing at least one portion of each of the pair of third element electrodes by selectively removing an upper portion of the pair of third element electrodes in the insulating film, and the fourth step includes a step of forming a coil having ends, each of which is connected to a corresponding third element electrode of the pair via a corresponding third opening of the pair, on the insulating film by patterning the conductive film.
In the method as described above, a coil with high L value that has been difficult to form by the conventional semiconductor process can be realized. Therefore, semiconductor elements for high frequency can be attained.
In the method for producing a semiconductor device of the present invention, it is preferable that the method includes a fifth step of forming a protective film having a property of repelling a conductive material so as to cover the first external electrode, the second external electrode and the connecting wire and then selectively removing an upper part of each of the first external electrode and the second external electrode in the protective film to form a fourth opening for exposing at least one portion of the first external electrode and a fifth opening for exposing at least one portion of the second external electrode, after the fourth step.
According to the method as described above, when mounting the semiconductor device on the motherboard, unfavorable electrical short-circuit is prevented between and the first external electrodes, the second external electrodes or the connecting wires and wirings or electrodes of the motherboard, and the connection can be easily performed between the first external electrodes or the second external electrodes and the wirings or the electrodes of the motherboard with a connecting member such as solder.
In the case where the method includes the fifth step, it is preferable that the fifth step includes a step of forming a first external electrode terminal connected to the first external electrode via the fourth opening immediately above the first external electrode and forming a second external electrode terminal connected to the second external electrode via the fifth opening immediately above the second external electrode.
According to the method as described above, the semiconductor device can be mounted on the motherboard very easily.
In the method for producing a semiconductor device of the present invention, it is preferable that the first step includes a step of forming a pair of third element electrodes electrically connected to the semiconductor element on the semiconductor substrate, that the method includes, between the first step and the second step, a step of forming a passivation film covering the surface of the semiconductor substrate except the first element electrode, the second element electrode and the pair of third element electrodes, and then forming a coil having ends, each of which is connected to a corresponding third element electrode of the pair, on the passivation film, and that the insulating film covers the passivation film and the coil.
According to the method as described above, the reliability of the semiconductor device can be improved further. A coil with high L value that has been difficult to form by the conventional semiconductor process can be realized by patterning the conductive pattern formed on the semiconductor substrate to form the coil, so that the semiconductor elements for high frequency can be attained.